This Composite Fe-C anode sputtering in a low-pressure arc discharge has been used to produce Fe-containing nanoparticles on a carbon matrix. Magnetic susceptibility as a function of background pressure has been measured. The data obtained showed the complex, no-monotonous dependency. The material synthesized at optimal pressure (maximal value of magnetic susceptibility) was investigated by means of transmission electron microscopy, X-ray diffraction and magnetometry. Size distribution function of iron containing nanoparticles has been measured. Chemical composition includes iron, iron carbide and carbon soot. Saturation magnetization have been measured and it was shown that the synthesized material is superparamagnetic. The physical processes resulting in the complex behavior of magnetic susceptibility are discussed.